Vibratory drive systems may be used in many applications. In the field of material processing, for example, vibratory drive systems may be used in screening apparatus and in some feeders and conveyors.
By way of example, mechanical screening involves separating particulate material, such as rocks, sand, or other aggregate material, by particle size. Screening is used in a variety of industries including mining, quarrying, mineral processing, agriculture and recycling. A conventional screening apparatus comprises a body that carries one or more decks of screen media. A vibratory drive system is provided for vibrating the body and decks. A known type of vibratory drive system includes multiple, eccentrically weighted, rotatable shafts, mechanically coupled together and driven by a common motor. Each shaft carries an eccentrically mounted mass, and the respective angular positions of the masses define a phase angle between shafts. The coupled shafts may rotate the same direction or in opposite directions and cause the screening apparatus to vibrate linearly, circularly or elliptically. The characteristics of the vibrations depend on the direction of rotation of the shafts and on the phase angle between the shafts.
A problem with conventional drive systems is that the shafts are typically mechanically locked together by, for example, gears or timing belts. Adjusting the phase angle in order to adjust the vibration characteristics, requires significant down-time for the screening apparatus and any machine of which it is part, since the drive system must be stopped and at least partly dismantled to allow an operator to make the necessary mechanical reconfiguration.
It would be desirable therefore to provide a screening apparatus with an improved drive system.